Vented plastic bag with filter medium

ABSTRACT

A vented plastic bag is adapted for containing a powdery product. The plastic bag includes a plurality of walls joined together and formed of a flexible plastic material. The walls define a fill opening for receiving the powdery product into the plastic bag. At least one of the bag walls defines a ventilation zone including a plurality of spaced-apart perforations. A filter medium overlies the ventilation zone and covers the plurality of perforations to substantially capture and retain the powdery product within the plastic bag during fill and ventilation.

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

This invention relates generally to heavy duty plastic bags, and morespecifically to a vented industrial shipping sack with an attachedfilter medium for capturing and retaining product, particularly duringfilling and venting. Vented bags are commonly used for packaging powderyproducts, such as powdered TiO2, ground gypsum, activated carbon, andthe like. Such bags are typically fabricated from LD, HD, or LLDpolyolefin sheet or tube stock, such as polyethylene or polypropylenehaving a thickness in the range of 3 to 12 mils. The sheet or tube stockmay be coextruded or monoextruded, and may be a single ply or multi-plymaterial. The multi-ply material may be multiple thicknesses of the samesheet or tube stock, or different materials to provide particularcharacteristics, such as strength, flexibility, UV resistance, or color.The sheet stock may also be woven or non-woven synthetic ornon-synthetic material. While the invention has particular applicationto vented bags with a capacity of from 20 to 100 pounds, the presentconcept can be applied to bags of any size and style.

There exists a present and long-felt need in the industry for a heavyduty industrial shipping sack for packaging powdery products. Oneprimary advantage of traditional paper-like (or fibrous) shipping sacksis their inherent ability to filter product during the filling process.Drawbacks to such bags, however, are substantial. For example, manypowdery products cannot tolerate fiber contamination common in a paperenvironment. Additionally, paper sacks are considerably weaker thanplastic, and often cannot withstand the rigors of external,environmental conditions. While use of a plastic bag is generallypreferable for increased strength and durability, common fill processeswhich force powdery product into the bag under pressure requireeffective ventilation and the ability to retain the product inside thebag during filling, venting, and shipping.

Prior art plastic shipping sacks with perforations have been used topackage a variety of products, but have limited use for powdery productsdue to their inability to properly retain product during filling andventilation. These bags typically have a rank-and-file arrangement ofrelatively large perforations. Plastic bags with much smallerperforations have had some success, but often either still allow smallparticles to exit the package, or worse, the small particles can plugthe perforations and not allow the air to evacuate. Other prior artplastic bags comprise multiple layers with off-set perforations. Whilethese type bags have had limited success, excessive powder is ofteneither captured in-between the multiple layers or escapes from the bagaltogether.

Outside of re-engineering the plastic bag, some in the industry haveinvested heavily in equipment designed to remove the air duringpackaging of powdery products. This equipment is expensive, and stilloften requires some sort of secondary ventilation.

SUMMARY OF INVENTION

Therefore, it is an object of the invention to provide a ventedindustrial shipping bag with an attached filter medium for capturing andretaining powdery product during filling and venting.

It is another object of the invention to provide a vented plasticshipping bag which is fabricated from plastic sheet or tube stock.

It is another object of the invention to provide a vented plastic bagwhich incorporates a fibrous, air-release filter medium.

It is another object of the invention to provide a vented plastic bagwhich incorporates a filter medium comprising a random arrangement ofvariable-size filter openings which resist clogging.

It is another object of the invention to provide a vented plastic bagwhich can withstand higher packaging temperatures (as compared tostandard polyethylene shipping sacks).

It is another object of the invention to provide a vented plastic bagwhich incorporates a fibrous and absorbent filter medium that acts todraw and trap moisture away from the packaged product, while allowingair release.

It is another object of the invention to provide a vented plastic bagwhich is applicable for packaging powdery products that can be readilydissolved along with the bag without ever opening the package.

It is another object of the invention to provide a vented plastic bagwhich is available in a version such that end users could incorporatetheir own selected micron-rated filter-ply films to custom manufacture,fill and seal their own packaging.

It is another object of the invention to provide a multi-layer packagingcomposite which is applicable for use with automatic form/fill/sealmachines.

It is another object of the invention to provide a method for filling aplastic bag with a powdery product.

These and other objects of the present invention are achieved in thepreferred embodiments disclosed below by providing a vented plastic bagadapted for containing a powdery product. The term “powdery product”refers to any loose product composed of or similar to powder and whichmay contain fines or other small particulate matter. The plastic bagincludes a plurality of walls joined together and formed of a flexibleplastic material. The term “joined” means either two formerly separatesheets connected together, or integrally formed by, for example, foldingover a sheet to form an edge. The walls define a fill opening forreceiving the powdery product into the plastic bag. At least one of theplastic bag walls defines a ventilation zone comprising a plurality ofspaced-apart perforations. A fibrous filter medium overlies theventilation zone and covers the plurality of perforations tosubstantially capture and retain the powdery product within the plasticbag during fill and ventilation. The term “fibrous” is defined broadlyherein to mean any material containing, consisting of, or resemblingfibers. Alternatively, the filter medium may comprise any non-fibrousmaterial which defines a similar random arrangement of variable-sizefiltration openings.

Preferably, the filter medium comprises a single-ply filter panel.

According to one preferred embodiment of the invention, the filter panelis affixed to the plastic bag along welded seams (and without needleopenings).

Preferably, the filter medium comprises a non-woven material.

According to one preferred embodiment of the invention, the filtermedium comprises a fibrous material selected from a group consisting ofpolyester felt, polypropylene microfiber, nylon monofilament,polyethylene, and PTFE.

Preferably, the micron rating of the filter medium is less than themicron rating of the perforations of the ventilation zone.

According to one preferred embodiment of the invention, the filtermedium has a nominal micron rating of less than 100.

According to another preferred embodiment of the invention, theperforations of the ventilation zone have a nominal micron ratinggreater than 500.

Preferably, the filter medium is positioned to reside between thepowdery product and ventilation zone. Alternatively, the filter mediummay reside adjacent the ventilation zone on an outside surface of thebag wall.

According to one preferred embodiment of the invention, a product-sidesurface of said filter medium is glazed to reduce fiber contamination ofthe powdery product.

In another embodiment, the invention is a method for filling a plasticbag with a powdery product. The method includes the steps of insertingthe powdery product into the plastic bag, and venting the plastic bag.During ventilation, air exiting the plastic bag is filtered using afibrous filter medium to substantially capture and retain the powderyproduct within the plastic bag.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects of the invention have been set forth above. Otherobjects and advantages of the invention will appear as the descriptionproceeds when taken in conjunction with the following drawings, inwhich:

FIG. 1 is a perspective view of a powder-filled plastic vented bagaccording to one preferred embodiment of the present invention;

FIG. 2 is a view of the vented bag laid flat prior to filling;

FIG. 3 is a fragmentary view of the vented bag with one bag wall cutaway and the filter medium partially pulled from the opposite,perforated bag wall;

FIG. 4 is a further fragmentary view of the vented bag with variouslayers shown in cross-section, and demonstrating the escape of airthrough the filter medium and perforated bag wall.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE

The present invention is described more fully hereinafter with referenceto the accompanying drawings, in which preferred embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be operative and enabling. Like numbers referto like elements throughout. Although specific terms are employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation. Unless otherwise expressly defined herein,such terms are intended to be given their broad ordinary and customarymeaning not inconsistent with that applicable in the relevant industryand without restriction to any specific embodiment hereinafterdescribed.

Referring now specifically to the drawings, a plastic vented bagaccording to a preferred embodiment of the present invention isillustrated in FIG. 1 and shown generally at reference numeral 10. Thevented bag 10 is especially applicable for packaging powdery products,such as powdered chemicals. The vented bag 10 may be formed in anydesired size and style including satchel-style valve bags, pillow-stylevalve bags, open mouth bags, and film type bags used by automaticform-fill-seal machines.

In the embodiment shown, the vented bag 10 comprises a valve bag whichis satchel-style pasted at both ends during its manufacture. The bag 10is preferably machine-fabricated from heavy duty polyolefin tube stock,and comprises opposing integrally-formed walls 1 1 and 12 defining a top14, bottom 15 and sides 16 and 17. When the bag walls 11, 12 are sealedto form the closed ends 14, 15, a tape of plastic is added to create thefilling valve (not shown) in one of the corners of the bag 10. Aflexible plastic sleeve 18 extends out of the valve and cooperates witha valve packer (e.g., air, auger, impeller, belt) to load product intothe bag 10. After filling, the sleeve 18 is typically folded and tuckedinto the valve. The valve bag 10 may be closed using a self-closinginternal valve, ultrasonic sealing, or other suitable means.

As best shown in FIGS. 1 and 2, in order to allow venting duringfilling, a number of spaced-apart perforations 21 are formed in the bag10 in an area of the wall 11 The perforations 21 are preferably spacedin a rank-and-file arrangement defining a ventilation zone which coversa majority of the wall 11 of the bag 10. According to one embodiment,the ventilation zone occupies greater than 25% of the entire surfacearea of the bag walls 11, 12. The size or “micron rating” of eachperforation 21 is relatively large to promote rapid expulsion of air.Preferably, the nominal micron rating is at least 100, and morepreferably, greater than 500. The “nominal” rating means that the bagwall 11 will capture substantially all particles larger than 100 micron,but will allow some percentage of particles larger than 100 microns toby-pass the perforations.

Referring to FIGS. 3 and 4, to prevent the escape of powdery product “P”through the relatively large perforations 21 during filling and ventingof the bag 10, a fibrous non-woven filter ply 25 is affixed to theplastic wall 11 by fabric welding, adhesive, or other means (outside ofsewing). The filter ply 25 is preferably joined to the bag 10 bycontinuous seams 27 and 28 along its longitudinal edges, and along itsend edges by welded end seams (not shown). Because there are no sewnholes in the bag 10 there is no particle by-pass through the seams 27,28. The filter ply 25 overlies the ventilation zone on either an insideor outside of the perforated plastic wall 11, and completely covers eachof the perforations 21 such that air exiting the vented bag 10 is firstfiltered to substantially capture and retain product “P” within the bag10. FIG. 4 demonstrates the evacuation of air “A” through the filter ply25 and perforated bag wall 11.

According to one preferred embodiment, the filter ply 25 comprises aspunbonded, non-woven polypropylene microfiber. Alternatively, thefilter ply 25 may comprise other fibrous or fiber-like materialsincluding paper, melt-blown polyethylene, nylon monofilament, polyesterfelt, or PTFE. The filter ply 25 may also comprise a non-fibrous,mechanically perforated, 2- or 3-dimensional substrate which defines asimilar random arrangement of clog-resistant, variable-size openings.Preferably, the filter ply 25 is a self-supported or scrim-supportedmaterial. To avoid fiber contamination, the product-side surface 25A ofthe filter ply 25 may be singed or glazed.

While the micron rating of the filter ply 25 will vary depending on userrequirements, the size of the filter openings in all cases will likelybe smaller than the wall perforations 21. For most powders, the nominalmicron rating will be less than 100. As indicated above, the micronrating selected determines the size of the particles captured as theproduct is filtered.

A plastic vented bag is described above. Various details of theinvention may be changed without departing from its scope. Furthermore,the foregoing description of the preferred embodiment of the inventionand the best mode of practicing the invention are provided for thepurpose of illustration only and not for the purpose of limitation-theinvention being defined by the claims.

1. A vented plastic bag adapted for containing a powdery product, saidplastic bag comprising: a plurality of walls joined together and formedof a flexible plastic material, said walls defining a fill opening forreceiving the powdery product into said plastic bag; at least one ofsaid bag walls defining a ventilation zone comprising a plurality ofspaced-apart perforations; and a fibrous filter medium overlying saidventilation zone and covering said plurality of perforations tosubstantially capture and retain the powdery product within said plasticbag during fill and ventilation.
 2. A vented plastic bag according toclaim 1, wherein said filter medium comprises a single-ply filter panel.3. A vented plastic bag according to claim 2, wherein said filter panelis affixed to said plastic bag along welded seams.
 4. A vented plasticbag according to claim 1, wherein said filter medium comprises anon-woven material.
 5. A vented plastic bag according to claim 1,wherein said filter medium comprises a fibrous material selected from agroup consisting of polyester felt, polypropylene microfiber, nylonmonofilament, polyethylene, and PTFE.
 6. A vented plastic bag accordingto claim 1, wherein said filter medium has a nominal micron rating ofless than
 100. 7. A vented plastic bag according to claim 6, wherein theperforations of said ventilation zone have a nominal micron ratinggreater than
 500. 8. A vented plastic bag according to claim 1, whereinsaid filter medium is positioned to reside between the powdery productand ventilation zone.
 9. A vented plastic bag according to claim 8,wherein a product-side surface of said filter medium is glazed to reducefiber contamination of the powdery product.
 10. A vented plastic bagadapted for containing a powdery product, said plastic bag comprising: aplurality of walls joined together and formed of a flexible plasticmaterial, said walls defining a fill opening for receiving the powderyproduct into said plastic bag; at least one of said bag walls defining aventilation zone comprising a plurality of spaced-apart perforations;and a filter medium overlying said ventilation zone and covering saidplurality of perforations to substantially capture and retain thepowdery product within said plastic bag during fill and ventilation,said filter medium defining a random arrangement of variable-sizefiltration openings.
 11. A vented plastic bag according to claim 10,wherein said filter medium comprises a single-ply filter panel.
 12. Avented plastic bag according to claim 11, wherein said filter panel isaffixed to said plastic bag along welded seams.
 13. A vented plastic bagaccording to claim 10, wherein said filter medium comprises a non-wovenmaterial.
 14. A vented plastic bag according to claim 10, wherein saidfilter medium comprises a fibrous material selected from a groupconsisting of polyester felt, polypropylene microfiber, nylonmonofilament, polyethylene, and PTFE.
 15. A vented plastic bag accordingto claim 10, wherein said filter medium has a nominal micron rating ofless than
 100. 16. A vented plastic bag according to claim 15, whereinthe perforations of said ventilation zone have a nominal micron ratinggreater than
 500. 17. A vented plastic bag according to claim 10,wherein said filter medium is positioned to reside between the powderyproduct and ventilation zone.
 18. A vented plastic bag according toclaim 17, wherein a product-side surface of said filter medium is glazedto reduce fiber contamination of the powdery product.
 19. A method forfilling a plastic bag with a powdery product, said method comprising thesteps of: inserting the powdery product into the plastic bag; ventingthe plastic bag; and during ventilation, filtering air exiting theplastic bag using a fibrous filter medium to substantially capture andretain the powdery product within the plastic bag.
 20. A methodaccording to claim 19, and comprising venting the plastic bag through aplurality of perforations formed with a wall of the bag.
 21. A methodfor filling a plastic bag with a powdery product, said method comprisingthe steps of: inserting the powdery product into the plastic bag;venting the plastic bag; and during ventilation, filtering air exitingthe plastic bag using a filter medium to substantially capture andretain the powdery product within the plastic bag, the filter mediumdefining a random arrangement of variable-size filtration openings. 22.A method according to claim 21, and comprising venting the plastic bagthrough a plurality of perforations formed with a wall of the bag.
 23. Amulti-layer packaging composite, comprising: a flexible plastic sheetmaterial comprising a plurality of spaced-apart perforations; and afibrous filter medium overlying said sheet material and covering saidplurality of perforations.
 24. A packaging composite according to claim23, wherein said filter medium comprises a single-ply filter panel. 25.A packaging composite according to claim 24, wherein said filter panelis affixed to said plastic sheet material along welded seams.
 26. Apackaging composite according to claim 23, wherein said filter mediumcomprises a non-woven material.
 27. A packaging composite according toclaim 23, wherein said filter medium comprises a fibrous materialselected from a group consisting of polyester felt, polypropylenemicrofiber, nylon monofilament, polyethylene, and PTFE.
 28. A packagingcomposite according to claim 23, wherein said filter medium has anominal micron rating of less than
 100. 29. A packaging compositeaccording to claim 28, wherein the perforations of said plastic sheetmaterial have a nominal micron rating greater than
 500. 30. A packagingcomposite according to claim 23, wherein said filter medium comprisingan inside surface residing adjacent said plastic sheet material and aglazed outside surface.
 31. A multi-layer packaging composite,comprising: a flexible plastic sheet material comprising a plurality ofspaced-apart perforations; and a filter medium overlying said sheetmaterial and covering said plurality of perforations, said filter mediumdefining a random arrangement of variable-size filtration openings. 32.A packaging composite according to claim 31, wherein said filter mediumcomprises a single-ply filter panel.
 33. A packaging composite accordingto claim 32, wherein said filter panel is affixed to said plastic sheetmaterial along welded seams.
 34. A packaging composite according toclaim 31, wherein said filter medium comprises a non-woven material. 35.A packaging composite according to claim 31, wherein said filter mediumcomprises a fibrous material selected from a group consisting ofpolyester felt, polypropylene microfiber, nylon monofilament,polyethylene, and PTFE.
 36. A packaging composite according to claim 31,wherein said filter medium has a nominal micron rating of less than 100.37. A packaging composite according to claim 36, wherein theperforations of said plastic sheet material have a nominal micron ratinggreater than
 500. 38. A packaging composite according to claim 31,wherein said filter medium comprising an inside surface residingadjacent said plastic sheet material and a glazed outside surface.